An exhaust gas aftertreatment device including a reduction catalyst that uses ammonia (a reduction-causing agent) obtained from a urea aqueous solution has been typically known for purifying exhaust gas from an internal combustion engine such as a diesel engine. The urea aqueous solution is pumped from a tank to an injector and injected from the injector into an exhaust pipe on an upper stream side of the reduction catalyst, whereby the urea aqueous solution is thermally decomposed by the heat of the exhaust gas. Ammonia is obtained by the thermal decomposition and the obtained ammonia is fed to the reduction catalyst to purify nitrogen oxides in the exhaust gas.
The urea aqueous solution stored in the tank is pumped by a pressure pump. The pressure pump includes a pump body, a filter element that filtrates the urea aqueous solution, and a housing that houses the pump body and the filter element. A lower side of the housing is screwed with a cap that closes an opening for attaching/detaching the filter element.
In such a pressure pump, when the filter element needs to be replaced, the cap is unscrewed from the housing to expose the opening on the lower side of the housing. A dedicated filter remover is inserted from the opening and is engaged with the filter element. By pulling the filter remover downward, the filter element is taken out of the housing.
An operation of engaging the filter element with the filter remover is conducted without visually checking an engaging portion at an end of the filter remover, since the engaging portion is inserted inside the housing. The filter remover is configured such that the hook-shaped engaging portion is elastically deformed while being inserted into the housing and is elastically restored by being engaged with the filter element. Accordingly, the filter remover needs to be pushed into the housing against an elastic restoration force of the engaging portion, which is a great burden on an operator. Consequently, it takes time and labor to replace the filter element.
In contrast, a filter device disclosed in Patent Literature 1 has been proposed. The filter device includes: a cylindrical filter element housed in a housing; and a cap (lid) engaged with a lower end of the filter element. The filter element and the cap are integrally assembled in advance. The filter element is housed in the housing when a female screw provided on the cap is screwed on a male screw provided on the housing. When the filter element needs to be replaced, the cap is unscrewed from the housing, whereby the filter element integrated with the cap is removed. Thus, the assembled cap and filter element are simultaneously replaced. Accordingly, no filter remover is required for replacing the filter element, which reduces time and labor for the operation.
Patent Literatures 2 and 3 disclose a filter remover configured to receive oil and the like leaking out in the replacement of the filter element. With such a filter remover, the operator can be prevented from getting caught in oil.